In order to provide better service experience for users in the heterogeneous network environment nowadays, Open Mobile Alliance (OMA) specifications support multi-UE and multi-address of a user, namely, an address of record of a user corresponds to multiple UEs owned by the user, or one user owns multiple UEs registered as different addresses of record. Such users may choose to use any of the registered UEs for communication. When such a user participates in a message session, the OMA specifications allow multiple UEs of the user to join the session simultaneously, and allow the user to hand over between UEs in the process of the session.
In a session process, this scenario may exist: The receiver instructs the sender to hand over to another UE, namely, another UE (referred to as after-handover UE) of the receiver joins the session in place of the UE before handover (referred to as before-handover). In the prior art, the handover between UEs may be implemented in the process of sending a message in the following way: First, a session path is created between the message sending UE and the before-handover UE. If the before-handover UE expects to hand the session over to another UE, the before-handover UE instructs the message sending UE to stop sending the message, and then sends a UE handover message to the message sending UE as an instruction of handover. Afterward, the message sending UE sets up a session with the after-handover UE according to the UE handover message, and then the before-handover UE quits the session to the message sending UE.
In the process of developing the present invention, the inventor finds that the message being received by the UE before handover may be lost during handover between UEs in the prior art.